Handle the common case of one chunk when calculating the uncompressed size

Reference #992

util/registry/gzipstream.py

@@ -16,6 +16,7 @@ class SizeInfo(object):
   def __init__(self):
     self.uncompressed_size = 0
     self.compressed_size = 0
+    self.is_valid = True
 
 def calculate_size_handler():
   """ Returns an object and a SocketReader handler. The handler will gunzip the data it receives,
@@ -23,17 +24,26 @@ def calculate_size_handler():
   """
 
   size_info = SizeInfo()
-
   decompressor = zlib.decompressobj(ZLIB_GZIP_WINDOW)
 
   def fn(buf):
+    if not size_info.is_valid:
+      return
+
     # Note: We set a maximum CHUNK_SIZE to prevent the decompress from taking too much
     # memory. As a result, we have to loop until the unconsumed tail is empty.
     current_data = buf
     size_info.compressed_size += len(current_data)
 
     while len(current_data) > 0:
-      size_info.uncompressed_size += len(decompressor.decompress(current_data, CHUNK_SIZE))
+      try:
+        size_info.uncompressed_size += len(decompressor.decompress(current_data, CHUNK_SIZE))
+      except:
+        # The gzip stream is not valid for some reason.
+        size_info.uncompressed_size = None
+        size_info.is_valid = False
+        return
+
       current_data = decompressor.unconsumed_tail
 
       # Make sure we allow the scheduler to do other work if we get stuck in this tight loop.